Powered reciprocating saws with coupled bone cutting reciprocating surgical saw blades are widely used in orthopedic surgery. Typically, reciprocating surgical saw blades are used to form longitudinal cuts in bone, in line with the reciprocating action of a surgical reciprocating motor. These surgical reciprocating motors typically operate at speeds from 8,000 cycles per minute to up to approximately 16,000 cycles per minute, and have a stroke or “excursion” of approximately 3 mm-6 mm. A reciprocating surgical saw blade typically includes a proximal end coupled to the coupling member of the surgical reciprocating motor, and a distal end with a cutting means including an array of bone cutting teeth. The dimensions of a cutting means of a reciprocating surgical saw blade typically range from 0.38 mm to 1.47 mm in thickness, from 5 mm to 15 mm in height, and from 12 mm to 90 mm in length.
The cutting means of reciprocating surgical saw blades are typically arrayed parallel to the longitudinal axis of the reciprocating surgical saw blade and parallel with the reciprocating motion of the powered surgical saw. In some instances, the cutting means may include bone cutting teeth arrayed upon a projection perpendicular to and extending away from the longitudinal axis of the reciprocating surgical saw blade. In other instances, there may be more than one cutting means.
Typically, teeth arrayed along the cutting means of reciprocating surgical saw blades are spaced apart (pitch between the teeth) in such a manner that anywhere from 4 to 12 teeth would engage a bone within the excursion of a single complete reciprocating cycle of the powered surgical saw. In other words, the distance between the teeth is typically always less than the stroke or excursion of the powered surgical saw. This arrangement of teeth distributes the work-load among more teeth, reducing the chip load placed upon any individual tooth, and more importantly reduces the possibility of placing undue stress or heat upon the bone being cut. Further to mitigate placing undue stress or heat upon the bone being cut by reciprocating surgical saw blades, such blades are typically quite thin with a medium or fine pitch between the teeth.
Reciprocating surgical saw blades with cutting means projecting perpendicular to and extending away from the longitudinal axis of the reciprocating surgical saw blade are often used to perform closed bone cuts wherein the kerf, the dimensions of the saw cut, created by the reciprocating surgical saw blade, is closed on all 4 sides of the bone cut, such that there is no entry slot or exit slot. As a result, in surgical applications requiring bone cuts with such closed profiles, additional stress is placed upon the bone being cut, because the reciprocating surgical saw blade runs up against a vertical wall of bone as the reciprocating surgical saw blade is fed downwardly into the closed slot and reciprocated by advancing and retracting within the closed slot.
Surgical applications calling for closed profile bone cutting are additionally complicated in that the width of the kerf of the closed profile is typically up to 6× wider than the width of the cutting means of a typical reciprocating surgical saw blade. Perpendicular protruding cutting blades are often used to place closed slots in bone to receive a stabilizing feature on a prosthetic orthopedic implant, which is critical to the long-term stability and success of that implant. However, simply widening the cutting means to 6× its typical width would place additional undue stress on the bone being cut, to the point of possible fracture of the bone. As such, in surgical applications calling for closed profile bone cutting, in order to reduce the stress placed upon the bone, reciprocating surgical saw blades with two parallel cutting means are typically used. Such a surgical saw blade 10, is shown in FIGS. 1A-1C, in accordance with the prior art. While stress being placed upon the bone may be reduced by using reciprocating surgical saw blades such as those of FIGS. 1A-1C, other surgical objectives may not be obtained. As an example, if the thicknesses of the two parallel cutting means 16 and 20, as shown in FIG. 1B, are acceptable in that they do not place undue stress on the bone being cut, each of the parallel cutting means 16 and 20 may not be wide enough to generate a kerf wide enough to receive the stabilizing feature of various implants. Also, if the thicknesses of the two parallel cutting means 16 and 20 are acceptable in that they do not place undue stress on the bone being cut and are simply spaced apart to the point that they are wide enough to generate a kerf wide enough to receive the stabilizing feature of various implants, there may be a ridge of bone left between the two parallel cutting means 16 and 20. The resulting bone ridge is especially difficult to remove when performing closed profile bone cutting.
What is needed is a reciprocating surgical saw blade suitable for operation with a surgical reciprocating motor that can perform closed profile bone cutting. The resulting kerf cut by the reciprocating surgical saw blade needs to be long enough and wide enough to receive the stabilizing features of an orthopedic implant, and the cutting means of the reciprocating surgical saw blade needs to form the kerf without placing undue stress on the bone being cut. The embodiments of the present disclosure answer these and other needs.